The research project in progress is designed to study the stages of arterial damage associated with intracerebral hemorrhages (strokes) in hypertensive rabbits. The development of structural changes preceding the end-stage formation of miliary aneurysms of the circular artery of the iris of hypertensive rabbits is subject to scrutiny by application of transmission and scanning electron microscopy. In addition, protein synthesis and replication by the cellular elements involved in developing arterial lesions of hypertensive rabbits are assayed by the application of sensitive autoradiographic techniques. The results of this research project should shed light on the mechanisms of arterial damage that lead to strokes associated with the hypertensive disease state in man.